Earth's environment can change drastically and challenge pilots as the fly across the globe. Pilots must be focused and ready to take-on any situation the comes their way. Sometimes there are situations that occur that can catch the pilot off guard. For example, wind shear can cause fatal damage to a pilot, their crew, and passengers if the pilot is not prepared. Wind shear can occur in the upper and lower levels of the atmosphere, but I will only be discussing the lower level atmospheric wind shear.

According to the Federal Aviation Administration (FAA) (2011), wind shear is defined as, "a rapid change in wind speed and direction over a short distance." In the lower portion of the atmosphere, wind shear can be caused by thunderstorms, temperature change, and obstruction. During thunderstorms, warm air rises on the outside of the storm and converge at the top of the storm. The warm air will then go to the center of the storm and rush to the surface at high speeds. Wind speeds can reach speeds of 100 knots per hour and can change direction up to 180 degrees. (FAA, 2011)

Temperature inversion wind shears usually occur in the southwestern region of the United States. (FAA, 2011)  During the night, the air is cooled at the surface up to a few hundred feet lower than the mountain range peaks. This cooling of air creates a temperature separation between the surface and the lower-level atmosphere. Once the warm air jet stream flows across the top of the calmer, cooler air, it creates wind shears that can change speed by 20-30 knots per hour and direction up to 90 degrees. (FAA, 2011)

Surface obstruction can also cause mini wind shears. The main obstruction that I am referring to are mountain ranges or larger buildings close to the runways. When a strong winds goes up and over mountain ranges or winding through buildings on the airports, there can be localized wind shears. Wind shears are to be expected by pilots when there are strong surface winds, the severity of the wind shear is completely unpredictable. (FAA, 2011)

Resources

FAA. (2011, August). Wind Shear. Retrieved from FAA Safety: https://www.faasafety.gov/files/gslac/library/documents/2011/Aug/56407/FAA%20P-8740-40%20WindShear%5Bhi-res%5D%20branded.pdf